There are many applications for pipe couplings where it is desired to couple two pipes together in a strong mechanical connection with a substantially fluid tight seal. A particular application for which the subject invention is especially adapted, is that of pipe joints in vehicle exhaust systems. In such an application, the pipe joints may be formed with abutting pipe ends to form a butt joint or pipes which are telescopically joined with overlapping ends to form a lap joint. In either type of joint, it has become a common practice to utilize a wide band clamp formed of sheet metal which is wrapped around the pipes to span the juncture between the pipes with the band being stretched around the pipes in close conformity therewith to form a good seal. Because of the relatively high temperature and mechanical stresses which occur in vehicle exhaust systems, the clamp band must be fabricated from a suitable grade of steel to provide the requisite strength for a long period of service. In some applications, such as heavy duty truck exhaust systems, the flat band clamp must join relatively large diameter pipes. One of the pipes may take the form of a flexible metal pipe having spiral corrugations while the other pipe may take the form of a rigid pipe which is joined therewith in either a butt joint or lap joint. In order to obtain intimate contact of the band with both pipe ends throughout its circumference for providing a good seal, it is necessary to subject the band to high tensile stress beyond the yield point or elastic limit. In applications where the band is of heavy gauge sheet metal, very large forces must be produced to provide the desired stretching of the band. Further, in some pipe joints of this type, one or both pipes will be either oversize or undersize, i.e. have an outside diameter which is either greater or smaller within certain tolerances than the nominal or mill diameter of the pipe. There is a need for a clamping mechanism capable of producing very high tensile forces on the band and yet which is easy to manipulate and tighten and which is adaptable to either undersize or oversize pipes.
The pipe coupling of this invention is an improvement upon the pipe coupling disclosed and claimed in U.S. Pat. No. 4,312,526 granted Jan. 26, 1982 to Thomas R. Cassel. In this patent a pipe coupling is disclosed for installation of pipes which are already butted or telescoped together. The coupling comprises a band clamp of the open sleeve type which is pre-formed into generally circular shape with end flanges at each end of the band for attachment with the clamping mechanism which stretches the band around the pipes. The clamping mechanism disclosed in this patent is capable of developing very large tensile forces on the band. In general, it comprises a spline having opposite concave surfaces disposed between the end flanges, a pair of force bars each having convex surfaces adapted to mate with the concave surfaces of the spline and disposed outboard of the respective end flanges. A pair of bolts extend through the force bars, flanges and spline for drawing the flanges inwardly against the spline and thus stretching the band around the pipes. The length of the band together with the end flanges in the clamping mechanism is such that when the bolts are fully tightened so that the end flanges are bottomed-out or seated against the concave surfaces of the spline, the band is stretched to the desired degree around the pipes.
The Hiemstra et al patent U.S. Pat. No. Re. 30,042 reissued July 10, 1979 discloses a pipe coupling which comprises a sheet metal band provided with reinforcing plates at each end with bolts extending through the plates to draw them together and stretch the band around the ends. The sheet metal of this coupling is in the form of a flat band with out-turned flanges which is wrapped around the pipe ends to bring the flanges in confronting relationship.
Other band clamps of this type are disclosed in the McGowen et al U.S. Pat. No. 4,142,743 granted Mar. 6, 1979 and in the McCord U.S. Pat. No. 4,463,975 granted Aug. 7, 1984.
A general object of this invention is to overcome certain disadvantages of the prior art.